Front body structure of vehicle

ABSTRACT

In a front body structure of a vehicle according to the present invention, satisfactory impact absorption can be achieved both at the time of offset collision and at the time of full-lapped collision. When a load applied to an offset-collided front side member from a front side of the vehicle is equal to or more than a predetermined value, the collided front side member is deformed. Thus, a front suspension member rotates. As a result, a bolt passing through the front suspension member fits into a branch of a slit of a rear mounting bracket disposed on the collided front side member, and the state in which the collided front side member is fixed to the front suspension member is maintained.

TECHNICAL FIELD

The present invention relates to a front body structure of a vehicle,and specifically to a front body structure of a vehicle for reducing theimpact acting on occupants at the time when the vehicle such as anautomobile comes into frontal collision.

BACKGROUND ART

Conventionally, in a front body structure of a vehicle for reducing theimpact acting on occupants at the time when the vehicle such as anautomobile comes into frontal collision, a front sub-frame is supportedby bolts to brackets which are fixed to a main frame and in whichrear-end opening slits are formed, and the bolts on the rear side slipfrom the rear-end openings of the slits at the time of frontalcollision. Accordingly, the main frame can be crushed without theinterruption of the front sub-frame. This structure is disclosed in, forexample, Japanese Patent Application Laid-Open (JP-A) No. 11-171046.

Further, in another front body structure of a vehicle for reducing theimpact acting on occupants at the time when the vehicle such as anautomobile comes into frontal collision, a front cross member extendingon a front edge of the vehicle along the transverse direction thereof isdivided at a substantially central portion of the front cross memberinto right and left two cross members, and a compass mechanism forsymmetrically restricting the rotational movement of the right and leftcross members with the respective substantially central portions thereofbeing as a rotational center is provided at a connecting portion betweenthe right and left cross members. This structure is disclosed in, forexample, JP-A No. 11-198854.

However, in the structure of JP-A No. 11-171046, even when the vehiclecomes into offset collision, the right and left bolts on the rear sideslip from the rear-end openings of the slits, and the impact is absorbedonly by the collided front side member. Therefore, the amount of impactabsorption in the case of offset collision is less than that in the caseof full-lapped collision (full collision), and satisfactory impactabsorption cannot be achieved. Further, in the structure of JP-A No.11-198854, the satisfactory impact absorption is limited by the problemof strength of the compass mechanism against a large collision load.

DISCLOSURE OF THE INVENTION

In view of the above facts, an object of the present invention is toobtain a front body structure of a vehicle, in which satisfactory impactabsorption can be achieved both at the time of offset collision and atthe time of full-lapped collision.

In order to solve the above problems, the front body structure of avehicle according to the present invention comprises: a pair of rightand left front side members disposed at a front portion of a vehiclebody along a longitudinal direction of the vehicle body; a connectingmember including front ends and rear ends in a transverse direction ofthe vehicle, the front ends and the rear ends being respectively fixedto front fixing portions and rear fixing portions of the pair of rightand left front side members; and fixing mechanisms disposed on the rightand left rear fixing portions, the fixing mechanisms releasing, when aload applied to the front side members from a front side of the vehicleis equal to or more than a predetermined value at a time of full-lappedcollision, a state in which the front side members are fixed to theconnecting member, and maintaining, at a time of offset collision, astate in which the collided front side member is fixed to the connectingmember.

When the vehicle comes into full-lapped collision, the state in whichthe front side members are fixed to the connecting member is released bythe fixing mechanisms disposed at the rear fixing portions of the frontside members and the connecting member. As a result, the right and leftfront side members receive the load and are deformed so that the impactcan be absorbed.

On the other hand, when the vehicle comes into offset collision, thestate in which the collided front side member is fixed to the connectingmember is maintained by the fixing mechanism disposed at the rear fixingportions of the collided front side member and the connecting member. Asa result, the collided front side member receives a part of the load andis deformed so that the impact can be absorbed, and the fixing mechanismalso receives a part of the load and is deformed so that the impact canbe absorbed. Further, the other front side member also receives a partof the load via the fixing mechanism and is deformed so that the impactcan be absorbed.

As a result, even in the case of offset collision, substantially thesame impact absorption effect as in the case of full-lapped collisioncan be obtained, and satisfactory impact absorption can be thus achievedboth at the time of offset collision and at the time of full-lappedcollision.

Further, in the front body structure of a vehicle according to thepresent invention, the connecting member may be a front suspensionmember.

Accordingly, since the front suspension member can be used as theconnecting member, there is no need to provide a particular connectingmember and the structure is thus simplified.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view showing a front body structure of a vehicle,according to an embodiment of the present invention, seen from a lowerside of the vehicle.

FIG. 2 is an exploded perspective view showing the front body structureof the vehicle, according to the embodiment of the present invention,seen from a lower front side of the vehicle at an angle.

FIG. 3 is an enlarged cross-sectional view seen along Line 3-3 in FIG.1.

FIG. 4 is a plan view showing a full-lapped collision state of the frontbody structure of the vehicle, according to the embodiment of thepresent invention, seen from the lower side of the vehicle.

FIG. 5 is a plan view showing an offset collision state of the frontbody structure of the vehicle, according to the embodiment of thepresent invention, seen from the lower side of the vehicle.

FIG. 6 is a graph showing reaction force characteristics in thefull-lapped collision state of the front body structure of the vehicle,according to the embodiment of the present invention.

FIG. 7 is a graph showing reaction force characteristics in the offsetcollision state of the front body structure of the vehicle, according tothe embodiment of the present invention.

FIG. 8 is a plan view showing a front body structure of a vehicle,according to another embodiment of the present invention, seen from alower side of the vehicle.

FIG. 9 is a plan view showing a front body structure of a vehicle,according to another embodiment of the present invention, seen from alower side of the vehicle.

FIG. 10 is a plan view showing a front body structure of a vehicle,according to another embodiment of the present invention, seen from alower side of the vehicle.

MOST PREFERRED EMBODIMENTS FOR IMPLEMENTING THE INVENTION

An embodiment of a front body structure of a vehicle according to thepresent invention will be described with reference to FIGS. 1 to 8.

In these figures, Arrows FR indicate the front direction of the vehicle,and Arrows UP indicate the upper direction thereof.

As shown in FIG. 1, in this embodiment, a pair of right and left frontside members 10, 12 are disposed at a front portion of a vehicle bodyalong the longitudinal direction thereof. A front bumper (not shown) issuspended between front ends 10A, 12A of the front side members 10, 12.Further, a front suspension member 20 serving as a connecting member issuspended between front portions of the pair of right and left frontside members 10, 12.

As shown in FIG. 2, the front suspension member 20 is structured suchthat a front cross member 26 and a rear cross member 28 are suspendedbetween two linear side rails 22, 24 extending along the longitudinaldirection of the vehicle. The front cross member 26 is shaped in an arcbulging toward the rear side of the vehicle, in a plan view. The rearcross member 28 is shaped in an arc bulging considerably toward thefront side of the vehicle, in a plan view.

Front mounting brackets 30, 32 are respectively disposed on lowersurfaces 10B, 12B of the front portions of the pair of right and leftfront side members 10, 12. Front ends 22A, 24A of the side rails 22, 24are respectively fixed to the front mounting brackets 30, 32 by bolts38, 40, which respectively pass through front rubber mounts 34, 36fitting in the front ends 22A, 24A of the side rails 22, 24.

Rear mounting brackets 50, 52 serving as fixing mechanisms arerespectively disposed on lower surfaces 10C, 12C of rear portions of thepair of right and left front side members 10, 12. Rear ends 22B, 24B ofthe side rails 22, 24 are respectively fixed to the rear mountingbrackets 50, 52 by bolts 58, 60, which respectively pass through rearrubber mounts 54, 56 fitting in the rear ends 22B, 24B of the side rails22, 24.

As shown in FIG. 3, each of the rear rubber mounts 54, 56 has awell-known structure in which an inner pipe 62 is connected to an outerring 64 via an elastic member 66. A center ring 68 for adjusting thespring constant is embedded in the elastic member 66. The frontsuspension member 20 has a closed cross-sectional structure in which anupper panel 20A and a lower panel 20B are integrally welded. Acup-shaped holder 70, into which the rear rubber mount 54 or 56 can befit from the lower side of the vehicle (the upper side of FIG. 3), iswelded between the upper panel 20A and the lower panel 20B.

Each of the rear mounting brackets 50, 52 is formed by bending a platemember and extends along the longitudinal direction of the vehicle body.The cross-sectional shape of the rear mounting brackets 50, 52 viewedfrom the longitudinal direction of the vehicle is a squared U-shapewhose opening is oriented to the upper side of the vehicle. Upper edgesof side walls 50A, 52A are respectively welded to side walls 10D, 12D ofthe front side members 10, 12.

In FIG. 3, Reference numeral 72 indicates a nut into which the bolt 58or 60 is screwed, and Reference numeral 74 indicates a washer.

As shown in FIG. 2, slits 82 opening toward the rear side of the vehicleare respectively formed in bottom walls 50B, 52B of the rear mountingbrackets 50, 52. Branches 82B (first branches) branching toward theinner rear side of the vehicle are respectively formed near rear-endopenings 82A of the slits 82.

Thus, as shown in FIG. 4, when the vehicle comes into full-lappedcollision with a wall 86 or the like, and the load applied to the rightand left front side members 10, 12 from the front side of the vehicle isequal to or more than a predetermined value, the bolts 58, 60 passingthrough the front suspension member 20 move toward the rear side of thevehicle (in Arrow A direction in FIG. 4) along the slits 82 of the rearmounting brackets 50, 52 disposed on the right and left front sidemembers 10, 12, and then the bolts 58, 60 come off the rear-end openings82A of the slits 82. Accordingly, the state in which the right and leftfront side members 10, 12 are fixed to the front suspension member 20 isreleased.

On the other hand, as shown in FIG. 5, when the vehicle comes intooffset collision with the wall 86 or the like, and the load applied tothe collided front side member 10 from the front side of the vehicle isequal to or more than a predetermined value, the collided front sidemember 10 is deformed. Thus, the front suspension member 20 rotates inArrow B direction in FIG. 5. As a result, the bolt 58 passing throughthe front suspension member 20 moves toward the rear side of the vehiclealong the slit 82 of the rear mounting bracket 50 disposed on the frontside member 10, and then the bolt 58 fits into the branch 82B of theslit 82. Accordingly, the state in which the collided front side member10 is fixed to the front suspension member 20 is maintained.

Next, operation of this embodiment will be described.

In this embodiment, as shown in FIG. 4, when the vehicle comes intofull-lapped collision with the wall 86 or the like, and the load appliedto the right and left front side members 10, 12 from the front side ofthe vehicle is equal to or more than a predetermined value, the bolts58, 60 passing through the front suspension member 20 move toward therear side of the vehicle (in Arrow A direction in FIG. 4) along theslits 82 of the rear mounting brackets 50, 52 disposed on the right andleft front side members 10, 12, and then the bolts 58, 60 come off therear-end openings 82A of the slits 82. Accordingly, the state in whichthe right and left front side members 10, 12 are fixed to the frontsuspension member 20 is released.

As a result, the right and left front side members 10, 12 receive thecollision load and are deformed so that the impact can be absorbed.Accordingly, when the spring constants of the right and left front sidemembers 10, 12 along the longitudinal direction of the vehicle arerespectively determined as K1 and K2, the reaction force at the time offull-lapped collision, F1, is proportional to the deformation stroke Sof the right and left front side members 10, 12, i.e., F1=K1•S+K2•S, asshown in the graph of FIG. 6. When K1=K2, then F1=2•K1•S.

On the other hand, as shown in FIG. 5, when the vehicle comes intooffset collision with the wall 86 or the like, and the load applied tothe collided front side member 10 from the front side of the vehicle isequal to or more than a predetermined value, the collided front sidemember 10 is deformed. Thus, the front suspension member 20 rotates inArrow B direction in FIG. 5. As a result, the bolt 58 passing throughthe front suspension member 20 fits into the branch 82B of the slit 82of the rear mounting bracket 50 disposed on the collided front sidemember 10. Accordingly, the state in which the collided front sidemember 10 is fixed to the front suspension member 20 is maintained.

As a result, the collided front side member 10 receives a part of thecollision load and is deformed so that a part of the impact can beabsorbed. In this case, the reaction force on the collided side, F2, isproportional to the deformation stroke S of the collided front sidemember 10, i.e., F2=K1•S, as shown in the graph of FIG. 7.

In the case of offset collision, since the state in which the collidedfront side member 10 is fixed to the front suspension member 20 ismaintained, the front suspension member 20 receives a part of thecollision load and is deformed so that a part of the impact can beabsorbed. In this case, when the spring constant of the front suspensionmember 20 along the longitudinal direction of the vehicle is determinedas K3, the reaction force of the front suspension member 20, F3, isproportional to the deformation stroke S, i.e., F3=K3•S.

Further, in the case of offset collision, the reaction force against therotation of the front suspension member 20, F4, is generated at theother front side member 12, wherein F4=α•S (α is a constant).

Accordingly, the total reaction force in the case of offset collision,F5, is proportional to the deformation stroke S of the collided frontside member 10, i.e., F5=F2+F3+F4=K1•S+K3•S+α•S, as shown in the graphof FIG. 7.

As a result, since the reaction force at the time of full-lappedcollision, F1=2•K1•S, if K3 (the spring constant of the front suspensionmember 20) and α (the constant of the reaction force against therotation of the front suspension member 20 in the front side members 10,12) are adjusted such that K1•S=K3•S+α•S is satisfied, F1 (the reactionforce at the time of full-lapped collision) becomes substantially equalto F5 (the total reaction force at the time of offset collision) (i.e.,F1≈F5). Thus, even in the case of offset collision, substantially thesame impact absorption effect as in the case of full-lapped collisioncan be obtained.

Accordingly, in this embodiment, satisfactory impact absorption can beachieved both at the time of offset collision and at the time offull-lapped collision.

Further, in this embodiment, since the front suspension member 20 can beused as a connecting member, there is no need to provide a particularconnecting member and the structure is thus simplified.

In the above embodiment, the case of elastic deformation has beendescribed by using the spring constants. However, even in the case ofdeformation due to actual collision, i.e., plastic deformation, the sameoperation and effect can be achieved.

The present invention has been described above in detail with regard tothe particular embodiment. However, the present invention is not limitedto this embodiment, and it is apparent to those skilled in the art thatother various embodiments are possible within the scope of the presentinvention. For example, in the above embodiment, the bolts 58, 60 arefit into the branches 82B of the slits 82 formed in the rear mountingbrackets 50, 52 serving as fixing mechanisms. However, in place of thebranches 82B, bolt-movement restraint mechanisms 82C for restraining themovement of the bolts 58, 60, such as irregular surfaces or largefriction surfaces, may be formed in inner peripheral surfaces of theslits 82, as shown in FIG. 8.

Further, as shown in FIG. 9, collision detection sensors 86, 88 may berespectively disposed near both ends of a front portion 84A of a vehiclebody 84 in the transverse direction of the vehicle, and lock bars 92serving as lock mechanisms, which open and close the opening ends 82A ofthe slits 82 of the rear mounting brackets 50, 52 due to operation ofactuators 90, may be respectively disposed near the opening ends of theslits 82. The actuator 90 of the offset-collided front side member 10 isoperated by a controller 94 based on detection signals from thecollision detection sensors 86, 88, and the lock bar 92 is therebyrotated in Arrow C direction so as to move from a position where theopening end 82A of the slit 82 is opened (illustrated by solid lines inFIG. 9) to a lock position where the opening end 82A of the slit 82 isclosed (illustrated by two-dotted chain lines in FIG. 9).

Furthermore, as shown in FIG. 10, the branches 82B branching toward theinner rear sides of the vehicle and branches 82D (second branches)branching toward the outer rear sides of the vehicle may be respectivelyformed near the rear-end openings 82A of the slits 82. In the event thatthe bolt 58 has passed through the rear-end opening 82A of the slit 82in the offset-collided front side member 10, the bolt 60 fits into thebranch 82D of the slit 82 in the other front side member 12 so that theimpact absorption effect at the time of offset collision can beprevented from being reduced.

In this embodiment, the front suspension member 20 is used as aconnecting member. However, the connecting member is not limited to thefront suspension member, and may be another member such as a frontsub-frame or an engine, or a special member.

INDUSTRIAL APPLICABILITY

As described above, the present invention can provide a front bodystructure of a vehicle, which has an advantage that satisfactory impactabsorption can be achieved both at the time of offset collision and atthe time of full-lapped collision.

1. A front body structure of a vehicle, comprising: a pair of right andleft front side members disposed at a front portion of a vehicle bodyalong a longitudinal direction of the vehicle body; a connecting memberincluding a pair of front end and a pair of rear ends in a transversedirection of the vehicle, the the front ends being respectively fixed tofront fixing portions and the rear ends being respectively fixed to rearfixing portions of the pair of right and left front side members; andfixing mechanisms disposed on the right and left rear fixing portions,the fixing mechanisms releasing, when a load applied to the front sidemembers from a front side of the vehicle is equal to or more than apredetermined value at a time of full-lapped collision, a state in whichthe front side members are fixed to the connecting member, andmaintaining, at a time of offset collision, a state in which thecollided front side member is fixed to the connecting member, whereinthe fixing mechanisms include slits extending parallel to the front sidemembers and first branches branching from vicinities of rear-endopenings of the slits toward inner rear sides of the vehicle, and fixingmembers of the connecting member can move in the slits and the firstbranches, and the first branches are structured such that, at the timeof offset collision, the fixing members fixing the connecting member tothe collided front side member move and fit into the first branch of theslit.
 2. The front body structure of a vehicle of claim 1, wherein theconnecting member is a front suspension member.
 3. The front bodystructure of a vehicle of claim 1, wherein the slits further includesecond branches branching toward outer rear sides of the vehicle.
 4. Thefront body structure of a vehicle of claim 1, wherein the secondbranches are structured such that, at the time of offset collision, thefixing members fixing the connecting member to the other front sidemember opposite to the collided front side member move and fit into thesecond branch of the slit.
 5. The front body structure of a vehicle ofclaim 1, structured such that reaction force of the right and left frontside members at the time of full-lapped collision becomes substantiallyequal to total reaction force at the time of offset collision.
 6. Thefront body structure of a vehicle of claim 5, structured such that, atthe time of offset collision, the connecting member receives a part ofthe collision load the collided front side member receives so that apart of impact can be absorbed.
 7. A front body structure of a vehicle,comprising: a pair of right and left front side members disposed at afront portion of a vehicle body along a longitudinal direction of thevehicle body; a connecting member including a pair of front ends and apair of rear ends in a transverse direction of the vehicle, the frontends being respectively fixed to front fixing portions and the rear endsbeing respectively fixed to rear fixing portions of the pair of rightand left front side members; and fixing mechanisms disposed on the rightand left rear fixing portions, the fixing mechanisms releasing, when aload applied to the front side members from a front side of the vehicleis equal to or more than a predetermined value at a time of full-lappedcollision, a state in which the front side members are fixed to theconnecting member, and maintaining, at a time of offset collision, astate in which the collided front side member is fixed to the connectingmember, wherein the fixing mechanisms include slits which extendparallel to the front side members and in which fixing members of theconnecting member can move, and movement restraint mechanisms forrestraining movement of the connecting member are formed in innerperipheral surfaces of the slits.
 8. A front body structure of avehicle, comprising: a pair of right and left front side membersdisposed at a front portion of a vehicle body alone a longitudinaldirection of the vehicle body; a connecting member including a pair offront ends and a pair of rear ends in a transverse direction of thevehicle, the front ends being respectively fixed to front fixingportions and the rear ends being respectively fixed to rear fixingportions of the pair of right and left front side members; and fixingmechanisms disposed on the right and left rear fixing portions, thefixing mechanisms releasing, when a load applied to the front sidemembers from a front side of the vehicle is equal to or more than apredetermined value at a time of full-lapped collision, a state in whichthe front side members are fixed to the connecting member, andmaintaining, at a time of offset collision, a state in which thecollided front side member is fixed to the connecting member, whereinthe fixing mechanisms include slits which extend parallel to the frontside members and in which fixing members of the connecting member canmove, and lock mechanisms for opening and closing opening ends areprovided near the slits, and at the time of offset collision, the lockmechanism closes the opening end of the slit of the fixing mechanismprovided on the collided front side member, based on detection signalsfrom collision detection sensors disposed at a front portion of thevehicle body.
 9. A front body structure of a vehicle, comprising: a pairof right and left front side members disposed at a front portion of avehicle body along a longitudinal direction of the vehicle body; aconnecting member including a pair of front ends and a pair of rear endsin a transverse direction of the vehicle, the front ends beingrespectively fixed to front fixing portions and the rear ends beingrespectively fixed to rear fixing portions of the pair of right and leftfront side members; and fixing mechanisms disposed on the right and leftrear fixing portions, the fixing mechanisms releasing, when a loadapplied to the front side members from a front side of the vehicle isequal to or more than a predetermined value at a time of full-lappedcollision, a state in which the front side members are fixed to theconnecting member, and maintaining, at a time of offset collision, astate in which the collided front side member is fixed to the connectingmember, wherein the fixing mechanisms include slits extending parallelto the front side members and first branches branching from vicinitiesof rear-end openings of the slits toward inner rear sides of thevehicle, and fixing members of the connecting member can move in theslits and the first branches.